1. Field of the Invention
The present invention relates to personal identification using bio information such as fingerprints. More particularly, the present invention relates to an authentication apparatus, an authentication method and an authentication program that allow distinction of a forgery such as a false finger by using a changing tendency of a form that a forgery such as a false finger has.
2. Description of the Related Art
In personal authentication, password authentication and an ID card authentication are used conventionally. These authentications have a high risk of theft. Thus, as more reliable personality authentication, authentication using bio information such as fingerprints is used. This authentication is utilized in various situations. Even if fingerprints are used, there still remains a risk by a false finger. In biometric authentication, authentication by a forgery is noted. Especially in fingerprints authentication, concerning false fingerprints (gummy fingerprints) made from gelatin, which appears in recent years, there is inconvenience that many fingerprint sensors regard the false finger as a bio finger.
As technique for excluding abuse by false fingerprints, there are patent documents such as Japanese Laid-open Patent Publication No. 2005-143804, International Publication Pamphlet No. WO2004/023999 and Japanese Laid-open Patent Publication No. 2002-279413. JP 2005-143804 discloses that a plurality of square wave input voltages having different frequencies are applied to a subject, output voltages which are responses thereto are measured to calculate impedance, and it is discriminated whether a finger is of a living body or not by investigating whether the impedance is within a range of reference impedance.
WO 2004/023999 discloses that when a plurality of images are continuously sampled, secrete that is secreted from exocrine glands of the organism skin is detected, and whether the subject is an organism or not is sensed by the existence of the secrete or not.
JP 2002-279413 A discloses that standard deviation of a pixel value of an input fingerprints image is calculated, the difference between the maximum value and the minimum value of the standard deviation values of N frames are given, and if the value thereof is at or larger than a threshold level, it is identified to be bio fingerprints and if below the threshold level, it is identified to be false fingerprints.
By the way, downsizing at low cost is difficult for the conventional art (JP 2005-143804) that needs dedicated hardware in order to prevent an authentication error by a forgery. Specifically, a fingerprint sensor improves in downsizing at low cost, but costs for detection of a false fingerprint since dedicated hardware is needed. In the conventional art (WO 2004/023999) detecting secrete, a dry finger that secretes less secrete may not prevent an authentication error. In the conventional art (JP 2002-279413) that the maximum value and the minimum value of the standard deviation are given from an input fingerprints image and the given values are compared with threshold level, a processor may be complexed and elaborate false fingerprints may not be determined.
Concerning such requests and problems, there is no disclosure nor suggestion thereof in JP 2005-143804, WO 2004/023999 and JP 2002-279413. No disclosure or suggestion about structure and so on for solving them is presented.